Uli, as it was explained to me round canopies are more forgiving of poor body position when deploying. If you are using a parachute for sport jumping the ram air 'chute is the only way to go, but for an emergency 'chute a novice user will have a better chance of getting a good deployment with the round canopy.
I'd ask your local rigger what they know, don't ask pilots what they "think".

-Doug